Lattice strain induced phase selection and epitaxial relaxation in crystalline GeTe thin film

•Lattice-match dependence in crystalline GeTe growth•The epitaxial relaxation induced by slight misfit strain•Crystalline GeTe is ferroelectric.•The local structure evolution during crystalline GeTe phase transition

We report that the lattice strain induced phase selection and epitaxial relaxation in crystalline GeTe thin films by pulsed laser deposition. The single-crystal substrates of MgO and BaF2 are designed to match the lattice of low-temperature α-GeTe phase and high-temperature β-GeTe phase, respectively. The structures of deposited GeTe films show lattice-match dependence rather than temperature dependence. Raman analysis indicates that the α-GeTe to β-GeTe ferroelectric phase transition accompanies an increase of local six-coordinated Ge atoms, which is analogous to the phase transition from amorphous to crystalline for memory application.